This application claims the priority of German Application No. 10 2006 058 402.3, filed Dec. 12, 2006, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a device for admixing a reducing agent into an exhaust gas flow of an internal combustion engine.
German published application DE 40 38 054 A1 describes a device for admixing a reducing agent into an exhaust gas flow of an internal combustion engine having an exhaust system and a dosing device for feeding the reducing agent into the exhaust system. Furthermore, the device contains a tripartite vaporizer for vaporizing the reducing agent. The first part, which the exhaust gas flows through, includes a metal honeycomb body, whose ribs may be heated by the exhaust gas. The heated ribs of the metal honeycomb body are situated so as to be oriented in the flow direction of the exhaust gas. An injection device bent by 90° projects into the exhaust system of the internal combustion engine to admix the reducing agent. Reducing agent is added to the exhaust gas by this injection device, which vaporizes on the heated ribs and thus becomes chemically active to eliminate nitrogen oxides in a special nitrogen oxide reduction catalytic converter. A urea-water solution and/or ammonia is preferably used as the reducing agent.
The device described in DE 40 38 054 A1 has the disadvantage of a relatively high flow resistance in the exhaust system, which may only be compensated for by a performance reduction of the internal combustion engine.
The present invention provides a device for admixing a reducing agent into an exhaust gas flow of an internal combustion engine that generates fewer flow losses.
According to the invention, a device is provided for admixing a reducing agent into an exhaust gas flow of an internal combustion engine having an exhaust system, a dosing device for feeding the reducing agent into the exhaust system, and at least one heating rib heatable by the exhaust gas, which is situated downstream from the dosing device in the exhaust system. The heating rib is oriented largely in a flow direction of the exhaust gas. The dosing device is arranged in or on a hollow body arranged on the exhaust system, an internal volume of which is connected to the exhaust system to conduct exhaust gas.
The present invention advantageously provides more favorable flow resistance and thus enhanced performance of the internal combustion engine.
Preferably, the reducing agent may be applied to the heating rib using the dosing device through the hollow body at an angle of approximately 20° and 90°.
In a further preferred embodiment, the heating rib is arranged in a separate pipe, which separate pipe may be situated in the exhaust system. Moreover, at least one further heating rib largely oriented parallel to the first heating rib, may be situated in the separate pipe. This has the advantage of improving the efficiency of the device.
In order to achieve substantially simultaneous vaporization of the heat reducing agent on the heating ribs, in a preferred embodiment the heating ribs are situated such that the reducing agent fed into the exhaust system is largely incident simultaneously on the heating ribs.
By preferably providing the heating ribs with a largely planar surface, the lowest flow losses are obtainable.
In a further preferred embodiment, the heating ribs are provided with a surface structure. In particular, the surface structure may project at most approximately 3 mm out of the planar surface of the heating ribs. This design further improves the efficiency of the device.
In yet another embodiment of the present invention, the separate pipe in which the heating rib is arranged includes a flange for fastening to the exhaust system. This advantageously provides a particularly easy to mount device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.